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ahbeetle1.jpg (18584 bytes) The Beetle That Ate Chicago

A new movie for the Annual Insect Fear Film Festival? Unfortunately, not. The Asian longhorned beetle (Anoplophora glabripennis) is a very real threat.

This 1.25-inch long, coal black beetle with irregular white spots on its back and 2-inch long antennae with white rings has invaded the United States, including Chicago, and it has a taste for our hardwood trees.

"I had heard about the Asian longhorned beetle when it was discovered in New York in 1996," says Larry Hanks, assistant professor of Entomology. "I was interested in learning more about it since I was studying a related species native to Australia. The Eucalyptus longhorned borer (Phoracantha semipunctata) has killed millions of eucalyptus trees in California since it was introduced in the 1980s."

"I thought that within 10 years we might find the Asian longhorned beetle in Chicago, and then I would have a chance to work on it." But last summer they were found in Ravenswood and several other areas in Chicago. "I think the beetles may actually have been in the Chicago area for at least 6 years. Although this is a flashy looking beetle, it is very hard to see in a tree, and probably went undetected."

This beetle is a serious pest in its native China where it kills hardwood trees. "We are fairly certain that the Asian longhorned beetle came to the United States in wooden shipping pallets from China." And this beetle has a big appetite.

"The Asian longhorned beetle prefers maple species— including Norway, red, silver, sugar, and boxelder—but it also attacks elm, black locust, green ash, mulberry, horse chestnut, poplars, and willows, or more than 60% of our street trees."

"Ironically, these tree species were planted to replace the elms killed by Dutch elm disease." This new pest may have equally catastrophic effects.

Although quarantines have been established and efforts are directed at trying to minimize the beetle’s spread, "it will be very difficult. The latitudes in China for its normal range correspond with the area from the Great Lakes to Cancun, Mexico."

Eradication of this pest is extremely unlikely. There are no natural predators. The larvae tunnel under the bark and into the wood, perhaps 6 inches under the surface, so topical insecticides are not effective. Systemic insecticides, even if effective, would be cost prohibitive. "It is a very pernicious pest."

Of the 35,000 species in this large family of beetles, many species seem to attack only stressed trees. WPWR Channel 50 Foundation in Chicago has awarded Hanks a grant to determine if the Asian longhorned beetle also uses stressed trees as hosts.

"If stress is required for infestation, then the Asian longhorned beetle probably won’t be a forest pest and it may not affect the maple syrup and tourist industries of the Northeast. Also, home-owners might be able to help prevent infestation in valuable trees by proper pruning, fertilization, etc."

To measure tree stress, Hanks and his students use a pressure bomb, a stainless steel chamber with a locking lid. They insert a leaf in the chamber with the petiole sticking through an opening in the lid. Then they apply pressure to the chamber until water comes out of the petiole, which is directly related to the water tension in the leaf. The higher the pressure, the more stressed the tree. After these baseline studies are conducted, Hanks and his associates will monitor patterns of infestation to determine whether the beetle prefers stressed trees—a process that will take years.

Hanks is interested in how adult behavior is influenced by its larval host requirements. Some beetle species feed on dying and dead trees. The nutritional quality of the host disintegrates quickly and there is intense competition for resources.

"We have found that the adults of such species are active fliers, quickly moving from tree to tree; adults feed for a short time, mate for very short periods, and lay eggs quickly."

The Asian longhorned beetle requires a living host. "As adults they will feed on the leaves, mate for hours, and may never leave their natal (or birth) tree. The adults are very lethargic. If you knock one out of the tree, it will just walk back and climb up the tree."

Multiple generations may be found in one tree, and it may take 5-6 years to kill a host, depending on the level of infestation. Understanding the beetles’ behavior may help in suggesting future control strategies.

The introduction of the Asian longhorned beetle into the US is a consequence of improved trade relations with China.

"Global commerce provides many opportunities for stow-away pests, and the problem will only get worse. There is a longhorned beetle in Japan that attacks pine trees. Imagine if it invades the States."

"These exotics are like the AIDS epidemic, and global shipping is like unprotected sex," says Hanks. "The only good thing is job security—at least for entomologists."

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Hanks2.jpg (14566 bytes) Hanks earned a BS in entomology from the University of California, Davis, in 1978, an MS in biology from the University of Nevada, Reno, in 1982, and a PhD in entomology from the University of Maryland, College Park, in 1991. He held a postdoctoral position at the University of California, Riverside, and then became an assistant research entomologist there. Hanks came to the University of Illinois in 1996.

Photographs of beetles courtesy of James E. Appleby.

School of Life Sciences

University of Illinois

This newsletter is published by the School of Life Sciences, University of Illinois at Urbana-Champaign. Editor: Jana Waite.  Send comments and suggestions to j-waite@life.uiuc.edu

Updated 11/05/99